Mobile data transmission and data services are constantly making progress, wherein such services provide various communication services, such as voice, video, packet data, messaging, broadcast, etc. In recent years, Long Term Evolution LTE™ has been specified, which uses the Evolved Universal Terrestrial Radio Access Network E-UTRAN as radio communication architecture according to 3GPP specification.
The technical field according to the present invention is mobile radio communications with focus on LTE and self optimizing networks SON, in particular mobility robustness optimization MRO.
The target of mobility robustness optimization is to optimize mobility related network configuration parameters, such as handover HO trigger parameters and HO thresholds or timers, in order to reduce radio link failures RLFs caused by mobility as well as handover failures HOFs.
In the prior art, 3GPP RAN WG3 (cf. prior art documents [1] and [2]) has specified so-called mobility robustness optimization failure types “Too late handover HO”, “Too early handover HO” and “Handover HO to Wrong Cell”, which help to decide for the right correction measure. These mobility robustness optimization failure types can be seen as mobility robustness optimization key performance indicators KPI.
That is, the measurements of too early handovers, too late handovers and to wrong cell handovers are obtained respectively by accumulating the number of failure events related to handover which are identified by the eNB according to the definitions in prior art document [1].
In addition, mobility robustness optimization determines the cell which is responsible for this failure. Normally this is the cell that has initiated the handover or has missed to initiate the handover. Mobility robustness optimization follows the rule that these key performance indicators are counted for those cells, more precisely the key performance indicators are counted per neighbor relation, e.g. if a “Too late HO” occurred at cell A and a user equipment UE managed to re-connect at cell B the key performance indicators is assigned to the neighbor relation “cell A to cell B”.
The counted mobility robustness optimization failure types are reported as performance management PM data to the network management (cf. prior art document [3]). The correction procedure can therefore be initiated by network management, i.e. in a centralized manner, or directly in the evolved NodeB (base station) eNB, i.e. in a decentralized manner. For latter case, the performance management data sent to the network management may be only for monitoring purpose.